U.S. patent number 11,329,709 [Application Number 16/696,023] was granted by the patent office on 2022-05-10 for beamforming architecture for scalable radio-frequency front end.
This patent grant is currently assigned to QUALCOMM Incorporated. The grantee listed for this patent is QUALCOMM Incorporated. Invention is credited to Shi Cheng, KeangPo Ricky Ho.
United States Patent |
11,329,709 |
Cheng , et al. |
May 10, 2022 |
Beamforming architecture for scalable radio-frequency front end
Abstract
An apparatus and a method for configuring antenna arrays for
scalable radio frequency (RF) architecture are dis-closed. A subset
of antenna arrays are grouped into K groups and a receive or
transmit weight vector is applied to each of the antenna arrays in
each of the K groups. A channel response is measured for each of
the antenna in the K groups. The response is summed for each group
and complex scaling factors are calculated based on the summed
response. Based on the scaling factors the antenna weight vectors
arc updated and the updated weight vectors arc applied to the
antenna arrays. The steps of grouping the antennas and refining the
weight vectors are performed till the antenna weight vectors reach
a steady point, i.e. the current antenna weight does not improve
the beamforming gain by a predetermined threshold in comparison to
the previous antenna weight.
Inventors: |
Cheng; Shi (Hillsboro, OR),
Ho; KeangPo Ricky (Hillsboro, OR) |
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
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Assignee: |
QUALCOMM Incorporated (San
Diego, CA)
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Family
ID: |
1000006294981 |
Appl.
No.: |
16/696,023 |
Filed: |
November 26, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200099431 A1 |
Mar 26, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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15763412 |
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10536207 |
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PCT/US2016/059301 |
Oct 28, 2016 |
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62248967 |
Oct 30, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B
7/0619 (20130101); H04B 7/0874 (20130101); H04B
7/0691 (20130101); H04B 7/0456 (20130101); H04B
7/0851 (20130101) |
Current International
Class: |
H04B
7/06 (20060101); H04B 7/08 (20060101); H04B
7/0456 (20170101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1389998 |
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Jan 2003 |
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CN |
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102594419 |
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Jul 2012 |
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CN |
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104023340 |
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Sep 2014 |
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CN |
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104158577 |
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Nov 2014 |
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CN |
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1265378 |
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Dec 2002 |
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EP |
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2002368520 |
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Dec 2002 |
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JP |
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2007258915 |
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Oct 2007 |
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JP |
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WO-2007095354 |
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Aug 2007 |
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WO |
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WO-2008077090 |
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Jun 2008 |
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WO |
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WO-2009085792 |
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Jul 2009 |
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WO |
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WO-2011063015 |
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May 2011 |
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WO |
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Other References
International Search Report and Written
Opinion--PCT/US2016/059301--ISA/EPO--dated Feb. 15, 2017. cited by
applicant .
Supplementary European Search Report--EP16860868--Search
Authority--Munich--dated Jul. 5, 2019. cited by applicant .
Supplementary Partial European Search Report--EP16860868--Search
Authority--Munich--dated Apr. 19, 2019. cited by applicant.
|
Primary Examiner: Vlahos; Sophia
Attorney, Agent or Firm: Holland & Hart LLP
Parent Case Text
CROSS REFERENCE
The present application for Patent is a divisional of U.S. patent
application Ser. No. 15/763,412 by CHENG, et al., entitled
"BEAMFORMING ARCHITECTURE FOR SCALABLE RADIO-FREQUENCY FRONT END"
filed Mar. 26, 2018, and claims priority to a 371 national phase of
International Patent Application No. PCT/US2016/059301 by Qualcomm,
Incorporated, et al., entitled, "BEAMFORMING ARCHITECTURE FOR
SCALABLE RADIO-FREQUENCY FRONT END," filed Oct. 28, 2016, which
claims priority to U.S. Provisional Patent Application No.
62/248,967 by Qualcomm, Incorporated et al., entitled "BEAMFORMING
ARCHITECTURE FOR SCALABLE RADIO-FREQUENCY FRONT END", filed Oct.
30, 2015; each of which is assigned to the assignee hereof, and
expressly incorporated by reference herein.
Claims
What is claimed is:
1. A method for refining transmit antenna weights, the method
comprising: grouping transmit antennas into a first plurality of
antenna groups, each antenna group of the first plurality of
antenna groups comprising a subset of the transmit antennas;
applying a transmit antenna weight vector to each antenna group of
the first plurality of antenna groups, the transmit antenna weight
vector specifying, for each antenna in a given antenna group of the
first plurality of antenna groups, a magnitude and phase gain to
apply to a signal transmitted by each antenna in the given antenna
group of the first plurality of antenna groups; obtaining a
measured response for each of the antenna groups of the first
plurality of antenna groups, from a receiver, when transmitting a
training signal with the transmit antenna weight vectors applied to
the antenna groups of the first plurality of antenna groups,
wherein obtaining the measured response for each of the antenna
groups is based at least in part on a measured response of each
transmit antenna in the given antenna group; updating the antenna
weight vectors for each group of transmit antennas based at least
in part on obtaining the measured response for each of the antenna
groups; applying the updated antenna weight vectors to the antenna
groups of the first plurality of antenna groups, the updated
antenna weight vectors specifying, for each antenna of the first
plurality of antenna groups, an updated magnitude and phase gain;
after application of the updated antenna weight vectors, regrouping
the transmit antennas into a second plurality of antenna groups
based at least in part on applying the transmit antenna weight
vector to each antenna group of the first plurality of antenna
groups and applying the updated antenna weight vectors to the
antenna group of the first plurality of antenna groups, wherein at
least one group of the second plurality of antenna groups is
different from at least one group of the first plurality of antenna
groups; and transmitting using the second plurality of antenna
groups comprising the regrouped transmit antennas having the
updated magnitude and phase gain.
2. The method of claim 1 wherein the measured response for each of
the antenna groups of the first plurality of antenna groups
comprises a summed response of each transmit antenna in the given
antenna group.
3. The method of claim 1 wherein obtaining the measured response
for each of the antenna groups includes receiving the measured
response by the receiver of each of the antenna groups.
4. The method of claim 3 wherein complex scaling factors for the
transmit antenna weight vector are computed based on the received
measured response.
5. The method of claim 1 wherein obtaining the measured response
for each of the antenna groups includes receiving computed complex
scaling factors for the antenna weight vectors based on the
measured response for each of the antenna groups from the
receiver.
6. The method of claim 1 further comprising: applying an additional
phase shift to each group of antennas according to columns of a
Hadamard matrix.
7. The method of claim 6 wherein obtaining the measured response
for each of the antenna groups comprises applying the Hadamard
matrix to the measured response for each of the antenna groups.
8. An apparatus comprising a data processing device having a
non-transitory storage medium and a digital signal processor
coupled with the non-transitory storage medium, the non-transitory
storage medium storing instructions that when executed by the
digital signal processor cause the processor to: group transmit
antennas into a first plurality of antenna groups, each antenna
group of the first plurality of antenna groups comprising a subset
of the transmit antennas; apply a transmit antenna weight vector to
each antenna group of the first plurality of antenna groups, the
transmit antenna weight vector specifying for each antenna in a
given antenna group of the first plurality of antenna groups, a
magnitude and phase gain to apply to a signal transmitted by each
antenna in the given antenna group of the first plurality of
antenna groups; obtain a measured response for each of the antenna
groups of the first plurality of antenna groups from a receiver
when transmitting a training signal with the transmit antenna
weight vectors applied to the antenna groups of the first plurality
of antenna groups, wherein obtaining the measured response for each
of the antenna groups is based at least in part on a measured
response of each transmit antenna in the given antenna group;
update the antenna weight vectors for each group of transmit
antennas based at least in part on obtaining the measured response
for each of the antenna groups; apply the updated antenna weight
vectors to the antenna groups of the first plurality of antenna
groups, the updated antenna weight vectors specifying, for each
antenna of the first plurality of antenna groups, an updated
magnitude and phase gain; after application of the updated antenna
weight vectors, regroup the transmit antennas into a second
plurality of antenna groups based at least in part on applying the
transmit antenna weight vector to each antenna group of the first
plurality of antenna groups and applying the updated antenna weight
vectors to the antenna groups of the first plurality of antenna
groups, wherein at least one group of the second plurality of
antenna groups is different from at least one group of the first
plurality of antenna groups; and transmit signaling using the
second plurality of antenna groups comprising the regrouped
transmit antennas having the updated magnitude and phase gain.
9. The apparatus of claim 8 wherein the measured response for each
of the antenna groups of the first plurality of antenna groups
comprises a summed response of each transmit antenna in the given
antenna group.
10. The apparatus of claim 8 wherein obtaining the measured
response for each of the antenna groups includes receiving the
measured response by the receiver for each of the antenna
groups.
11. The apparatus of claim 10 wherein complex scaling factors for
the transmit antenna weight vector are computed based on the
received measured response.
12. The apparatus of claim 8 wherein obtaining the measured
response for each of the antenna groups includes receiving computed
complex scaling factors for the antenna weight vectors based on the
measured response for each of the antenna groups from the
receiver.
13. The apparatus of claim 8 further comprising: applying an
additional phase shift to each group of antennas according to
columns of a Hadamard matrix.
14. The apparatus of claim 13 wherein obtaining the measured
response for each of the antenna groups comprises applying the
Hadamard matrix to the measured response for each of the antenna
groups.
15. An apparatus comprising a data processing device for refining
transmit antenna weights, the data processing device comprising: a
circuit to group transmit antennas into a first plurality of
antenna groups, each antenna group of the first plurality of
antenna groups comprising a subset of the transmit antennas; a
circuit to apply a transmit antenna weight vector to each antenna
group of the first plurality of antenna groups, the transmit
antenna weight vector specifying for each antenna in a given
antenna group of the first plurality of antenna groups, a magnitude
and phase gain to apply to a signal transmitted by each antenna in
the given antenna group of the first plurality of antenna groups; a
circuit to obtain a measured response for each of the antenna
groups of the first plurality of antenna groups, from a receiver,
when transmitting a training signal with the transmit antenna
weight vectors applied to the antenna groups of the first plurality
of antenna groups, wherein obtaining the measured response for each
of the antenna groups is based at least in part on a measured
response of each transmit antenna in the given antenna group; a
circuit to update the antenna weight vectors for each group of
transmit antennas based at least in part on obtaining the measured
response for each of the antenna groups; a circuit to apply the
updated antenna weight vectors to the antenna groups of the first
plurality of antenna groups, the updated antenna weight vectors
specifying, for each antenna of the first plurality of antenna
groups, an updated magnitude and phase gain; a circuit to regroup,
after application of the updated antenna weight vectors, the
transmit antennas into a second plurality of antenna groups based
at least in part on applying the transmit antenna weight vector to
each antenna group of the first plurality of antenna groups and
applying the updated antenna weight vectors to the antenna groups
of the first plurality of antenna groups, wherein at least one
group of the second plurality of antenna groups is different from
at least one group of the first plurality of antenna groups; and a
circuit to transmit using the second plurality of antenna groups
comprising the regrouped transmit antennas having the updated
magnitude and phase gain.
Description
BACKGROUND
1. Field of the Disclosure
The present disclosure relates generally to beamforming
architecture for a scalable RF front end, and more specifically to
refining receiver and transmitter antenna weight vectors for
enhancing Radio-Frequency (RF) system performance.
2. Description of the Related Art
Beamforming technology has been extensively used in the wireless
(i.e. radio frequency) and millimeter wave application space to
increase the directional antenna array gain. The increase in
directional antenna array gain facilitates a better quality of
signal transmission and reception. Products using wireless
technologies such as cellphones, laptops, etc., include multiple
transmit and multiple receive antennas to transmit and receive a
single spatial stream. To increase the antenna array gain,
conventional beamformers use a fixed set of weight (amplitude and
phase) to direct the antenna arrays. Adaptive beamformers generally
adjust the weight based on signal responses they receive from the
antenna arrays.
Typically, the beamformers, adaptive or conventional, are designed
for a fixed number of transmit or receive antennas. The beamforming
hardware is designed for the worst case, i.e. maximum number of
transmit/receive antennas, although all of the antennas may not be
used for communication, thus increasing the overall system
cost.
SUMMARY
Implementations of the present disclosure relate to an apparatus
and method for configuring arrays of transmit and receive antennas
for beamforming for a variable number of antennas. The number of
antennas in the transmit or receive arrays are not necessarily
fixed, and thus may be variable, such that the RF antenna
architecture is scalable. To configure transmit or receive antenna
arrays, the antennas are partitioned into K groups. A current
transmit or receiver antenna weight is applied to the transmit or
receiver antennas of each of the K groups.
A response, e.g., a summed response, of each of the transmit or
receiver antennas of a group, to the current weight vector is
measured. Based on the measurements, complex scaling factors are
calculated to adjust the current transmit or receiver antenna
weights for each group such that the output power (receiver or
transmit) is maximized. The updated weights are applied to the
antennas of each of the K groups. After applying the updated
weights, the receive or transmit antenna arrays may be regrouped.
The process may be repeated in multiple rounds. Rounds of the
process can be repeated until the transmit or receiver antenna
arrays are configured to output maximum power or another stopping
criterion is met. The refining iteration may alternate between
transmit and receive antenna refinement rounds. The process may be
restarted in response to a detected condition or criteria.
In a particular, aspect, the invention includes a method for
refining receiver antenna weights, which comprises grouping the
receiver antennas into a first plurality of antenna groups. Each
antenna group of the first plurality of antenna groups comprises a
subset of the receiver antennas. A receiver antenna weight vector
is applied to each antenna group. The receiver antenna weight
vector specifies, for each antenna in a given antenna group, a
magnitude and phase gain to apply a signal received by each antenna
in a given antenna group. A response of each of the antenna groups
is measured as the training signal is received and the receiver
antenna weight vectors are applied. Complex scaling factors for the
antenna weight vectors based on the measured responses are applied.
The receiver antenna weight vectors are updated based o the
computed complex scaling factors. The updated antenna weight
vectors are applied to the group of receiver antennas.
An aspect pertains to an apparatus comprising a data processing
device having a non-transitory storage medium and a digital signal
processor coupled with the non-transitory storage medium. The
non-transitory storage medium stores instructions that, when
executed by the Digital Signal Processor (DSP), cause the processor
to group receiver antennas into a first plurality of antenna
groups, each antenna group of the first plurality of antenna groups
comprises a subset of the receiver antennas. The instructions also
cause the DSP to apply a receiver antenna weight vector to each
antenna group, the receiver antenna weight vector specifying for
each antenna in a given antenna group, a magnitude and phase gain
to apply to a signal received by each antenna in the given antenna
group; measure a response of each of the antenna groups when
receiving a training signal and apply the receiver antenna weight
vectors; compute complex scaling factors for the antenna weight
vectors based on the measured responses; update the receiver
antenna weight vectors based on the computed complex scaling
factors; and apply the updated antenna weight vectors to the group
of receiver antennas.
Another aspect pertains to an apparatus comprising a data
processing device for refining transmit antenna weights, which
comprises a logic circuit to group transmit antennas into a first
plurality of antenna groups; each antenna group of the first
plurality of antenna groups comprises a subset of the transmit
antennas. The device also comprises a logic circuit to apply a
transmit antenna weight vector to each antenna group; the transmit
antenna weight vector specifies, for each antenna in a given
antenna group, a magnitude and phase gain to apply to a signal
received by each antenna in the given antenna group. The device
also comprises a logic circuit to obtain a response of each of the
antenna groups from the receiver when transmitting a training
signal and to apply the transmit antenna weight vectors. The device
also comprises a logic circuit to update the antenna weight vectors
for the group of transmit antennas and a logic circuit to apply the
updated antenna weight vectors to the group of transmit
antennas.
An aspect pertains to a method for refining transmit antenna
weights, comprising grouping the transmit antennas into a first
plurality of antenna groups. Each antenna group of the first
plurality of antenna groups comprises a subset of the transmit
antennas. The method also comprises applying a transmit antenna
weight vector to each antenna group. The transmit antenna weight
vector specifies, for each antenna in a given antenna group, a
magnitude and phase gain to apply to a signal transmitted by each
antenna in the given antenna group. The method comprises obtaining
a response of each of the antenna groups from the receiver, when
transmitting a training signal and applying the transmit antenna
weight vectors, updating the antenna weight vectors for the group
of transmit antennas and applying the updated antenna weight
vectors to the group of transmit antennas.
Another aspect pertains to an apparatus comprising a data
processing device having a non-transitory storage medium and a
digital signal processor coupled with the non-transitory storage
medium. The non-transitory storage medium stores instructions that
when executed by the digital signal processor cause the processor
to group transmit antennas into a first plurality of antenna
groups; each antenna group of the first plurality of antenna groups
comprises a subset of the transmit antennas. The instructions also
cause the process to apply a transmit antenna weight vector to each
antenna group, where the transmit antenna weight vector specify,
for each antenna in a given antenna group, a magnitude and phase
gain to apply to a signal received by each antenna in the given
antenna group. The instructions also cause the process to obtain a
response of each of the antenna groups from the receiver when
transmitting a training signal and apply the transmit antenna
weight vectors. The instructions also cause the process to update
the antenna weight vectors for the group of transmit antennas and
to apply the updated antenna weight vectors to the group of
transmit antennas. Logic circuits can be implemented by programming
a Digital Signal Processor (DSP) with instructions that can be
retrieved from one or more memories. Such circuits can use and/or
reuse elements that form or are used to form other circuits. A DSP
can be implemented using reconfigurable circuitry, such circuitry
of a Field Programmable Gate Array.
BRIEF DESCRIPTION OF THE DRAWINGS
The teachings of the embodiments of the present disclosure can be
readily understood by considering the following detailed
description in conjunction with the accompanying drawings.
FIG. 1 is a block diagram of beamforming architecture for scalable
RF front end, according to one embodiment.
FIG. 2 is a flowchart illustrating steps configuring transmit and
receive antennas for beamforming, according to one embodiment.
FIG. 3 is a flowchart illustrating steps for refining receiver
antennas, according to one embodiment.
FIG. 4 is a flowchart illustrating steps for refining transmit
antennas, according to one embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
The Figures (FIG.) and the following description relate to
preferred embodiments of the present disclosure by way of
illustration only. Reference will now be made in detail to several
embodiments of the present disclosure, examples of which are
illustrated in the accompanying figures. It is noted that wherever
practicable similar or like reference numbers may be used in the
figures and may indicate similar or like functionality. One skilled
in the art will readily recognize from the following description
that alternative embodiments of the structures and methods
illustrated herein may be employed without departing from the
principles of the disclosure described herein.
FIG. 1 is a block diagram of a beamforming architecture for a
scalable RF front end system 100, according to one embodiment. The
RF front end system includes an RF transmitter located on one
device and a RF receiver located on a second device. While FIG. 1
shows an example system 100 including one transmitter on one device
and one receiver on a second device in other embodiments each
device may include a transmitter and a receiver. The two devices
communicate by transmitting and receiving RF signals via the
transmitter (TX) and the receiver (RX) antennas sent over a channel
represented by the channel matrix H. The RF transmitter includes
one or more transmit antennas 120 v.sub.i,0 , . . . , v.sub.i,n, a
power amplifier that is connected to each transmit antenna 118, RF
front end processing modules 110 such as a digital signal
processing (DSP) module 112, a digital to analog converter (DAC)
114 and a mixer 116 on the transmitter side. Additionally the RF
receiver includes one or more receiver antennas 140 u.sub.i,0, . .
. , u.sub.i,n, RF front end processing modules 130 on the receiver
side such as an amplifier 132, a mixer 134, analog to digital
converter (ADC) 136 and a digital signal processing (DSP) module
138.
The RF transmitter converts a lower intermediate frequency (IF)
signal to a high frequency radio frequency (RF) signal and
transmits it over the transmit antenna array 120. The DSP module
118 on the transmitter side performs signal processing tasks such
as digital modulation, filtering, baseband beamforming processing
for every recursion stage and other such digital processing. Most
of the signal processing is done on a digital signal and it is
converted to an analog signal by a digital to analog converter
(DAC) module 112 before it is sent to the other transmitter front
end modules. The mixer 116 mixes the incoming signal with a radio
frequency signal to generate the RF signal for transmission. The
power amplifier 116 converts the low power RF signal to a larger
significant power for transmission via the transmit antenna array
120.
The channel between each transmitting and receiving pair of
antennas is modeled as a single channel. The channel matrix H for
the multiple transmit/receive antennas includes the vector
representation of the input-output relationship of each of the
transmitter/receiver antenna pair given by the single channel model
of each pair.
The RF signal is received by the set of receiver antennas 140 and
the signal is further processed by the receiver front end 130 to
convert the RF signal to a baseband signal. The amplifier 132
amplifies the desired signal while it rejects the unwanted signals.
The mixer 134 mixes the incoming signal with a signal that has a
fixed offset from a carrier frequency to produce a baseband signal.
In some embodiments, the mixer and amplifier may be cascaded and an
IF signal may be generated between RF and baseband. The analog to
digital converter (ADC) 136 module converts the analog baseband
signal to a digital signal for further processing by the DSP module
138 in the receiver. The DSP module 138 can perform processing
operations such as baseband beamforming processing and other such
configuration operations.
In one embodiment, the DSP module 112 and the DSP module 138 each
comprise one or more processors and a non-transitory
computer-readable storage medium storing instructions that when
executed by the one or more processors cause the one or more
processors to perform the operations described herein (e.g., the
processes described in FIGS. 2-4 below). In an alternative
embodiment, the transmitter and/or the receiver may include digital
logic instead of or in addition to the DSP module 112 and DSP
module 138 respectively for carrying out the processes described
herein whole or in part.
For beamforming, the set of transmit 120 and receive antenna 140
arrays are configured to maximize the signal to noise ratio (SNR)
of the received signal. FIG. 2 is a flowchart illustrating steps
for configuring transmit and receive antennas for beamforming,
according to one embodiment.
The configuring of antenna arrays starts 205 with determining 210
if the current receiver antenna weight vectors are at a steady
point. In one embodiment, the steady point is the global optimum
point for maximum system performance. In another embodiment, the
steady point is the local optimum point for the system performance
that cannot be changed by small perturbation of the antenna weight
vectors. The steady point for the receiver weight vectors may be a
temporary steady point for a given transmit antenna weight vectors.
The steady point for the receiver antenna weight vectors may be a
permanent steady point that is the optimal point regardless of
different choices of the transmit weight vector. In practical
implementation, the steady point may be determined where the
current receiver antenna weight vectors do not improve the
beamforming gain by a predetermined threshold. If the receiver
antenna vectors are not at the steady point, the receiver antennas
are further refined 215 by performing the method described in FIG.
3 below. If the receiver antenna weight vectors reach a steady
point, a determination is made 220 if the current transmit antenna
weight vectors are at a steady point. If they are not at the steady
point, the transmit antennas are further refined 225 by performing
the method described in FIG. 4. If the transmit antenna weight
vectors reach a steady point, a determination is made if the
current beamforming gain meets 230 the predetermined number of
iterations. If the current beamforming gain meets the target (e.g.
predefined or predetermined) number of iterations. If the above
condition is met, the process of refining the antenna weight
vectors is stopped 240. Otherwise, the iteration count is increased
by one and the process of refining restarts from step 205.
FIG. 3 is a flowchart illustrating steps for configuring an array
of receiver antennas for beamforming, according to one embodiment.
In this process, receiver antenna weight vectors are refined
iteratively, and each recursion involves the following steps.
Initial antenna weight vectors are received 305 for Nr receiver
antennas. The Nr receiver antennas are partitioned 310 into K
groups by the DSP module, according to one embodiment. The
partitioning varies in every recursion round, i.e. at least one of
the K groups base a different set of receiver antennas in
consecutive recursion rounds. Let R.sub.1, . . . , R.sub.K denote
the set of the antenna indices of each group.
The channel response is measured for each of the receiver antenna
groups based on their response on application of the current
receiver antenna weight vector u(R.sub.K)* when the current
transmitter antenna weight vectors applied at the transmitter are
fixed at v(Tk) at the transmitter. The measurement for each group
represents the summed response for the antennas in each group. To
perform the response measurements, a different scaling factor on
each group of antenna weight is applied, and different set of
measurements are performed. Herein, y.sub.r denotes the column
vector of the measurements with each element corresponding to an
individual measurement. The combined measurements are formed based
on the equation below:
.function..function. .function..function..function..function.
##EQU00001## where W is typically a matrix with K orthonormal
columns and at least K rows, and with a rank of K, and y.sub.r is
the combined measurement of the receiver antenna groups,
u(R.sub.1).sup.H . . . u(R.sub.K).sup.H is the application of the
current receiver antenna weight vector to the set of receiver
antennas and h.sub.v(R.sub.1), . . . , h.sub.v(R.sub.K) corresponds
to the channel responses on each antenna of the K groups. On the
mth measurement, the actual weight of the kth group of antenna is
the conjugate of u(R.sub.K) multiplied by the factor w.sub.m,k,
which is the element in the mth row and kth column of W.
There are multiple embodiments for measuring the channel response
that use training sequences. In one embodiment, the training
sequences are specific sequences that are sent from the TX and RX.
In another embodiment, the training sequences follow a data payload
of a packet as the post-amble. In another embodiment, the training
sequences are the preamble portions of a packet that may or may not
follow with a data payload. In the case that the training sequence
is the preamble of a packet without a data payload, it may be
preceded by an announcement of the training sequence.
The orthonormal set of vectors are post processed based on the
equation below to calculate the receiver responses from each group
of the K groups of the RX antennas.
.times..function..times..function..function..times..function.
##EQU00002## where z.sub.1, . . . , z.sub.k represents the overall
channel response for the group of RX antennas, where H in the
W.sup.H denotes a Hermitian transpose of W (i.e. taking a transpose
of a matrix and then taking a complex conjugate of each entry). An
example of W is a Hadamard matrix, i.e. a square matrix whose
elements are either +1 or -1. This makes the matrix multiplication
simple, since it is now just an addition of the elements of the
matrix it is being multiplied with, i.e. an addition of the
responses of the elements of y.sub.r. In practice, the necessary
condition is that the matrix W is of full column rank, i.e. the
rank of the matrix W is the same as its number of columns. With
this necessary condition, the matrix W.sup.H is replaced with the
corresponding pseudoinverse of W.sup.+=(W.sup.HW).sup.-1W.sup.H
Based on the measurements, a set of scaling factors .alpha..sub.1,
. . . , .alpha..sub.K are computed 325 to adjust the receiver
antenna weight vector in each group. The scaling factor can be a
complex number that includes the phase and amplitude adjustment or
a real number indicating that includes only an amplitude
adjustment.
The scaling factor is calculated to maximize the metric
|u.sup.Hh.sub.v|, that represents the output power of the group of
RX antennas for the channel matrix H when the transmit weight
vector v is applied at the transmitter, i.e. .alpha..sub.1, . . . ,
.alpha..sub.K=argmax|u.sub.new.sup.Hh.sub.v| where
u.sub.new(R.sub.k)=.alpha..sub.ku(R.sub.k), k=1, . . . , K, and
u.sub.new.sup.Hu.sub.new=1.
The scaling factor is calculated as follows:
.times.'.times..times.'' ##EQU00003## where
s.sub.k=u(R.sub.k).sup.Hu(R.sub.k), i.e. the normalized receiver
power, and the normalization constrain implies
.SIGMA..sub.k'=1.sup.ks.sub.k'=1.
The base receiver antenna vectors are updated 330 based on the
equation u.sub.new(R.sub.k)=.alpha..sub.ku(R.sub.k),
The updated receiver antenna weight u=u.sub.new is applied 335 to
the receiver antennas. If necessary, the receiver antennas are
regrouped 340 and recursive steps 315-340 are repeated.
The metric |u.sup.HHv| representing output power of the group of RX
antennas for the channel matrix H is improved in every recursion.
By adjusting the group partition of the receiver antennas in each
recursion round, the overall optimization is achieved. An important
processing in this method is the optimization of the scaling
factors for K antenna groups. The recursion optimizes only K
factors at a time, and the same measurement and calculation engine
is reused to adjust to different number of antennas. The refining
process is scalable such that if the number of antennas changes,
the antenna group partition is updated, and the rest of the process
is recursively repeated on the partitioned antennas. If the number
of antennas increases, as long as the number of groups remains the
same by having more antennas in each group, the beamforming method
remains the same since it depends on number of groups.
The beamforming method here includes weights that have both the
amplitude and phase, that are adjusted based on the measurement of
responses and the scaling factors. In another embodiment, the
weights may include only the phase component. In the phase only
weight case, the phase of the factors z.sub.k may be used without
the need to obtain the factors of .alpha..sub.K.
An example method is explained below for a receiver that includes 4
antennas. The channel response measurement can be performed by the
receiver turning on each antenna at a specified time and performing
a measurement. However, the receiver SNR may be improved by turning
on all 4 antennas simultaneously. Here, a Hadamard matrix is used
for the matrix W as follows:
##EQU00004##
Statistically, the received signal obtained is 4 times larger than
a single receiver signal. In one embodiment, the antennas use the
received vector of [1, 1, 1, 1], [1, -1, 1, -1], . . . , row by row
to obtain the measurement. In another embodiment, the antennas may
use the received vector of [u.sub.1, u.sub.2, u.sub.3, u.sub.4],
[u.sub.1, -u.sub.2, u.sub.3, -u.sub.4], [u.sub.1, u.sub.2,
-u.sub.3, u.sub.4], and [u.sub.1, -u.sub.2, -u.sub.3, u.sub.4] for
channel measurement. The two methods are equivalent and obtain
similar results.
In the scalable method, the 4 antennas are split to form two
groups. The training may be based on the matrix of
##EQU00005##
If the initial receiver phase vector is u.sup.(0)=[u.sub.1.sup.(0),
u.sub.2.sup.(0), u.sub.3.sup.(0), u.sub.4.sup.(0)], the first set
of two groups may be [1, 2] and [3, 4] and the training is based on
[u.sub.1.sup.(0), u.sub.2.sup.(0), u.sub.3.sup.(0),
u.sub.4.sup.(0)] and [u.sub.1.sup.(0), u.sub.2.sup.(0),
-u.sub.3.sup.(0), -u.sub.4.sup.(0)]. The inverse vectors should
obtain two new weights of [z.sub.1.sup.(1), z.sub.2.sup.(1)] for a
new vector of
.times..times..times..times. ##EQU00006## and u.sup.(1)=
.sup.(1)/.parallel. .sup.(1).parallel.=[u.sub.1.sup.(1),
u.sub.2.sup.(1), u.sub.3.sup.(1), u.sub.4.sup.(1)].
After training is performed on the first set of two groups, in a
subsequent iteration, training is performed on a second set groups
allocated as [1, 4] and [2, 3], for example, using
[u.sub.1.sup.(1), u.sub.2.sup.(1), u.sub.3.sup.(1),
u.sub.4.sup.(1)] and [u.sub.1.sup.(1), -u.sub.2.sup.(1),
-u.sub.3.sup.(1), u.sub.4.sup.(1)] to obtain [z.sub.1.sup.(2),
z.sub.2.sup.(2)], and
.times..times..times..times..times..times..times. ##EQU00007##
After normalization, a third iteration may be performed using a
third set of two groups allocated as [1, 3] and [2, 4].
FIG. 4 is a flowchart illustrating steps for configuring an array
of transmitter antennas for beamforming, according to one
embodiment. The transmitter antenna weight vectors are refined
iteratively, and each recursion involves the following steps.
Initial antenna weight vectors are received 405 for N1 transmit
antennas. N1 transmit antennas are partitioned 410 into K groups by
the DSP module of the RF transmitter. The partitioning varies in
every recursion round such that at least one of the K groups has a
different set of transmit antennas for consecutive recursion
rounds. Let T.sub.1, . . . , T.sub.K denote the set of the antenna
indices of each group.
A signal is transmitted 420 from the transmit antennas to the
receiver antennas with the transmit weight vector v(T.sub.k)*
applied 420 to each of the transmit antennas in the K groups. and
the transmitter obtains 425 results from the receiver for each of
the K groups of transmit antennas. The channel response is measured
for each of the receiver antenna in each of the K groups based on
their response on application of the current transmit antenna
weight vector v(T.sub.k)* when the receiver antenna weight vectors
are fixed at u(R.sub.K)*. To perform the response measurements, a
different scaling factor on each group of antenna weight is
applied, and a different set of measurements are performed.
Denoting y.sub.t as the column vector of the measurements, each
element corresponds to an individual measurement. y.sub.t can be
formed based on the equation below.
.function..function. .function..function..function..function.
##EQU00008## where W is typically a matrix with K orthonormal
columns and at least K rows, and with a rank of K, y.sub.t is the
conjugate of the combined measurement of the transmit antenna
groups, v(T.sub.1).sup.H, . . . , v(T.sub.K).sup.H are the
conjugate of the current transmit antenna weight vector to the set
of transmit antennas and h.sub.u(T.sub.1), . . . h.sub.u(TK)
corresponds to the conjugate of the channel responses of each
antenna of the K groups. On the mth measurement, the actual weight
of the kth group of antenna is conjugate of v(T.sub.k) multiplied
by the factor w.sub.m,k, which is the element in the mth row and
kth column of W.
The orthonormal set of vectors are post processed based on the
equation below to calculate the receiver responses for each group
of the K groups of the TX antennas:
.times..function..times..function..function..times..function.
##EQU00009## where z.sub.1, . . . , z.sub.k represents the overall
channel response for the group of the TX antennas, where .sup.H in
the W.sup.H denotes a Hermitian transpose that takes a transpose of
a matrix and then taking a complex conjugate of each entry. An
example of W is a Hadamard matrix that is a square matrix whose
elements are either +1 or -1. This makes the matrix multiplication
simple, since it's now just an addition of the elements of the
matrix it is being multiplied with, i.e. an addition of the
responses of the elements of y.sub.t.
Based on the measurements, a set of scaling factors .alpha..sub.l,
. . . , .alpha..sub.K are computed 425 to adjust the transmit
antenna weight vector in each group. The scaling factor can be a
complex number, i.e. it includes the phase and amplitude adjustment
or a real number indicating that includes an amplitude
adjustment.
In one embodiment, the measurements of the channel response
z.sub.1, . . . , z.sub.k are transmitted from the receiver to the
transmitter (e.g., via a backchannel) and the transmitter computes
the scaling factors. Alternatively, the receiver may compute the
scaling factors and provide the scaling factors directly to the
transmitter.
The scaling factor is calculated to maximize the metric
|v.sup.Hh.sub.u| which represents the output power of the group of
TX antennas of the channel matrix H when the transmit weight vector
u is applied at the receiver, i.e. .alpha..sub.1, . . .
,.alpha..sub.K=argmax|v.sub.new.sup.Hh.sub.u| where
v.sub.new(T.sub.k)=.alpha..sub.kv(T.sub.k), k=1 . . . K and
v.sub.new.sup.Hv.sub.new=1
The scaling factor is calculated as follows:
.times.'.times..times.'' ##EQU00010## where
s.sub.k=v(T.sub.k).sup.Hv(T.sub.k) the normalized transmit power,
and the normalization constraint implies
.SIGMA..sub.k'=1.sup.Ks.sub.k>=1.
The base transmit antenna vectors are updated 430
v.sub.new(R.sub.k)=.alpha..sub.kv(R.sub.k), or .alpha..sub.1, . . .
,.alpha..sub.K=argmax|v.sub.new.sup.Hh.sub.u| where
v.sub.new(T.sub.k)=.alpha..sub.kv(T.sub.k), k=1 . . . K, and
v.sub.new.sup.Hv.sub.new=1. The updated transmit antenna weight
v=v.sub.new is applied 435 to the transmit antennas. If necessary,
the transmit antennas are regrouped 440 and recursive steps are
repeated.
Example benefits and advantages of the disclosed configurations
include configuring multiple transmit and receive antenna arrays
for a scalable RF architecture. The primary benefit includes
eliminating the need for additional RF front end processing modules
when the antenna arrays are scaled to include additional antennas.
This scalability helps in cost reduction.
Additionally, the method of regrouping and refining the antenna
arrays continuously improves the antenna gain, and if the grouping
of antennas is done correctly, it leads to a global convergence of
the antenna weight vectors to achieve the maximum beamforming
antenna gain. This results in a high performance signal
transmission across the transmitter and receivers of devices.
Throughout this specification, plural instances may implement
components, operations, or structures described as a single
instance. Although individual operations of one or more methods are
illustrated and described as separate operations, one or more of
the individual operations may be performed concurrently, and
nothing requires that the operations be performed in the order
illustrated. Structures and functionality presented as separate
components in example configurations may be implemented as a
combined structure or component. Similarly, structures and
functionality presented as a single component may be implemented as
separate components. These and other variations, modifications,
additions, and improvements fall within the scope of the subject
matter herein.
Certain embodiments are described herein as including logic or a
number of components, modules, or mechanisms, for example, as
illustrated in FIG. 1. Modules may constitute either software
modules (e.g., code embodied on a machine-readable medium or in a
transmission signal) or hardware modules. A hardware module is
tangible unit capable of performing certain operations and may be
configured or arranged in a certain manner. In example embodiments,
one or more computer systems (e.g., a standalone, client or server
computer system) or one or more hardware modules of a computer
system (e.g., a processor or a group of processors) may be
configured by software (e.g., an application or application
portion) as a hardware module that operates to perform certain
operations as described herein.
In various embodiments, a hardware module may be implemented
mechanically or electronically. For example, a hardware module may
comprise dedicated circuitry or logic that is permanently
configured (e.g., as a special-purpose processor, such as a field
programmable gate array (FPGA) or an application-specific
integrated circuit (ASIC) to perform certain operations. A hardware
module may also comprise programmable logic or circuitry (e.g., as
encompassed within a general-purpose processor or other
programmable processor) that is temporarily configured by software
to perform certain operations. It will be appreciated that the
decision to implement a hardware module mechanically, in dedicated
and permanently configured circuitry, or in temporarily configured
circuitry (e.g., configured by software) may be driven by cost and
time considerations.
The various operations of example methods described herein may be
performed, at least partially, by one or more processors, e.g.,
processor 112, 138, that are temporarily configured (e.g., by
software) or permanently configured to perform the relevant
operations. Whether temporarily or permanently configured, such
processors may constitute processor-implemented modules that
operate to perform one or more operations or functions. The modules
referred to herein may, in some example embodiments, comprise
processor-implemented modules.
The one or more processors may also operate to support performance
of the relevant operations in a "cloud computing" environment or as
a "software as a service" (SaaS). For example, at least some of the
operations may be performed by a group of computers (as examples of
machines including processors), these operations being accessible
via a network (e.g., the Internet) and via one or more appropriate
interfaces (e.g., application program interfaces (APIs).
The performance of certain of the operations may be distributed
among the one or more processors, not only residing within a single
machine, but deployed across a number of machines. In some example
embodiments, the one or more processors or processor-implemented
modules may be located in a single geographic location (e.g.,
within a home environment, an office environment, or a server
farm). In other example embodiments, the one or more processors or
processor-implemented modules may be distributed across a number of
geographic locations.
Some portions of this specification are presented in terms of
algorithms or symbolic representations of operations on data stored
as bits or binary digital signals within a machine memory (e.g., a
computer memory). These algorithms or symbolic representations are
examples of techniques used by those of ordinary skill in the data
processing arts to convey the substance of their work to others
skilled in the art. As used herein, an "algorithm" is a
self-consistent sequence of operations or similar processing
leading to a desired result. In this context, algorithms and
operations involve physical manipulation of physical quantities.
Typically, but not necessarily, such quantities may take the form
of electrical, magnetic, or optical signals capable of being
stored, accessed, transferred, combined, compared, or otherwise
manipulated by a machine. It is convenient at times, principally
for reasons of common usage, to refer to such signals using words
such as "data," "content," "bits," "values," "elements," "symbols,"
"characters," "terms," "numbers," "numerals," or the like. These
words, however, are merely convenient labels and are to be
associated with appropriate physical quantities.
Unless specifically stated otherwise, discussions herein using
words such as "processing," "computing," "calculating,"
"determining," "presenting," "displaying," or the like may refer to
actions or processes of a machine (e.g., a computer) that
manipulates or transforms data represented as physical (e.g.,
electronic, magnetic, or optical) quantities within one or more
memories (e.g., volatile memory, non-volatile memory, or a
combination thereof), registers, or other machine components that
receive, store, transmit, or display information.
As used herein any reference to "one embodiment" or "an embodiment"
means that a particular element, feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment. The appearances of the phrase
"in one embodiment" in various places in the specification are not
necessarily all referring to the same embodiment.
Some embodiments may be described using the expression "coupled"
and "connected" along with their derivatives. For example, some
embodiments may be described using the term "coupled" to indicate
that two or more elements are in direct physical or electrical
contact. The term "coupled," however, may also mean that two or
more elements are not in direct contact with each other, but yet
still co-operate or interact with each other. The embodiments are
not limited in this context.
As used herein, the terms "comprises," "comprising," "includes,"
"including," "has," "having" or any other variation thereof, are
intended to cover a non-exclusive inclusion. For example, a
process, method, article, or apparatus that comprises a list of
elements is not necessarily limited to only those elements but may
include other elements not expressly listed or inherent to such
process, method, article, or apparatus. Further, unless expressly
stated to the contrary, "or" refers to an inclusive or and not to
an exclusive or. For example, a condition A or B is satisfied by
any one of the following: A is true (or present) and B is false (or
not present), A is false (or not present) and Bis true (or
present), and both A and Bare true (or present).
In addition, use of the "a" or "an" are employed to describe
elements and components of the embodiments herein. This is done
merely for convenience and to give a general sense of the
invention. This description should be read to include one or at
least one and the singular also includes the plural unless it is
obvious that it is meant otherwise.
Upon reading this disclosure, those of skill in the art will
appreciate still additional alternative structural and functional
designs for a system and a method for configuring antenna arrays
for beamforming in scalable RF architecture through the disclosed
principles herein. Thus, while particular embodiments and
applications have been illustrated and described, it is to be
understood that the disclosed embodiments are not limited to the
precise construction and components disclosed herein. Various
modifications, changes and variations, which will be apparent to
those skilled in the art, may be made in the arrangement, operation
and details of the method and apparatus disclosed herein without
departing from the spirit and scope defined in the appended
claims.
* * * * *